The present invention is directed, in general, to polishing pads and, more specifically, to a method of manufacturing a polishing pad using a focused beam.
In the fabrication of semiconductor components, the various devices are formed in layers upon an underlying substrate, such as silicon. In such semiconductor components, it is desirable that all layers, including insulating layers, have a smooth surface topography, since it is difficult to lithographically image and pattern layers applied to nonuniform surfaces. To this end, conventional chemical/mechanical polishing (CMP) has been developed for providing planar semiconductor topographies. Typically, a given semiconductor wafer may be planarized several times, such as upon completion of each metal layer.
The CMP process involves holding, and optionally rotating, a thin, reasonably flat, semiconductor wafer against a rotating polishing pad. The wafer may be repositioned radially within a set range as the polishing pad is rotated across the surface of the wafer. The polishing surface, which conventionally includes a polyurethane material affixed to a platen, is wetted by a chemical slurry, under controlled chemical, pressure, and temperature conditions. The chemical slurry contains selected chemicals which etch or oxidize selected surfaces of the wafer during the CMP process in preparation for their removal.
The more uniformly the chemical and mechanical agents remove the material during the polishing process, the better planarization of the polished surface of the semiconductor wafer. However, in this process it is important to remove a sufficient amount of material to provide a planar surface, without removing an excessive amount of underlying materials. As a result, uniform material removal is particularly important in today""s submicron technologies where the layers between device and metal levels are constantly getting thinner.
Because of the importance of the uniform removal of material, the manufacture of semiconductor wafer polishing pads has become a critical part of the overall manufacturing process. Conventional polishing pads for use in the CMP process are typically formed by adhering a polyurethane polishing surface, or other suitable polymer material, to a foam or felt pad impregnated with the same or similar polymer material. However, before the gluing may take place, an initial step in the manufacture of such polishing pads is cutting the polishing pad from a large cylinder, called a xe2x80x9ccake,xe2x80x9d composed of that material. This step of the manufacturing process is typically referred to as xe2x80x9cskiving.xe2x80x9d Unfortunately, conventional techniques used to skive the polishing pad from the cake are believed to be problematic.
Accordingly, what is needed in the art is a method of manufacturing a polishing pad that does not suffer from the numerous deficiencies of the methods found in the prior art.
To address the above-discussed deficiencies of the prior art, the present invention provides a method of manufacturing a semiconductor wafer polishing pad using a beam, and a system incorporating the method. In one embodiment, the method includes providing a cake that is susceptible to beam ablation, and skiving a polishing pad from the cake using the beam. In an advantageous embodiment, the cake is comprised of polyurethane.
In exemplary embodiments of the present invention the beam may be a laser, for example an excimer laser, and may be pulsed along the cutting line where the cake will be skived. In these embodiments, the beam may have an intensity of about 400 mJ, a wavelength ranging from about 193 nm to about 308 nm, and a frequency ranging from about 250 Hz to about 800 Hz. In addition, if the beam is pulsed, the duration of each pulse ranges from about 10 ns to about 50 ns.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.